Fig. 5. Native PA28αβ is able to modify the patterns of peptides generated from IGF-1 in a way similar to recombinant PA28α. Digestion of IGF-1 and separation of peptides were performed as in Figure 4, except that PA28αβ was used at a 3-fold lower concentration than PA28α (0.5 µM instead of 1.5 µM).